Cloud droplets in the atmosphere have an organic component which has been shown to form a monolayer film at the air-water interface of the cloud droplet and the atmosphere. The process by which a cloud droplet film will oxidise and the persistence or loss of an oxidised organic film from the air-liquid interface of a cloud droplet is not well quantified. To determine the surface properties of a cloud droplet film during atmospheric oxidation a measurement of a kinetic variable, the concentration of material comprising an organic film, during reaction with atmospheric radicals was required. The coupling of a Langmuir trough with a neutron reflectometer allows the measurement of the surface coverage of a monolayer in unison with measurement of the monolayer surface pressure. The technique of coupling a Langmuir trough with neutron reflectometry is used extensively for research into the properties of surfactants for industrial and medicinal use. This thesis builds on the work of King et al., (2009) and King et al., (2010), whom produced the first neutron reflectivity measurements of atmospheric proxy monolayers reacting with ozone. This is the first thesis detailing the neutron reflectometry measurement from an atmospheric perspective. Measurements were taken of representative fatty acid molecules which have atmospheric relevance (stearic acid, oleic acid and methyl oleate) as well as measurements of phospholipid molecules which are potential parent species for the fatty acids found in atmospheric waters (I ,2-dipalmitoyl-sn-glycero-3-phosphocholine). The mono layers were reacted with aqueous phase OH radical and with gas-phase ozone to assess the kinetics of the oxidation of the monolayers at the air-water interface.